The present invention relates to methods and devices used to review and record physiological data, such as blood pressure and electrocardiogram data. More particularly, the invention relates to a method and a system of reducing the amount of physiological data delivered to devices used to review and analyze the data, thereby reducing the complexity of and resources required in those devices.
Modern medical practice involves monitoring a variety of physiological activity. In electrocardiography and other types of patient monitoring, current data is often compared to historical data in order to observe the trends and changes in the data. As can be appreciated, the amount of data collected in monitoring activities can be very large. For example, in ambulatory ECG monitoring, changes in QRS waves are identified by visually comparing current and previous measurements. With current technology, the QRS data must be stored locally at a computer or workstation. The amount of data acquired is generally on the order of 40MB or more. The amount of time required to transfer this amount of data from the acquisition device to the analysis workstation makes historical comparisons impractical, except with very fast (and, therefore, expensive) data links and high performance workstations.
In addition to the data volume problem noted above, another deficiency with many current monitoring techniques is that the review and analysis device must process raw data and have appropriate software sophisticated enough to display the data. Data from physiological monitoring devices is typically transferred in a raw fonnat, i.e., the actual sample points from the A-to-D converters or filtered A-to D values. This technique requires any computer that displays the information to understand the raw data format. Generally, only very powerful workstations and computers with a complete set of programs are able to process raw data. Thus, many present systems used to analyze data are relatively expensive.
Accordingly, it would be desirable to have a method and system for reducing the amount of data handled by analysis devices to reduce the complexity of and resources required by those devices.
The invention provides a method and system that formats physiological data before transmission to a monitoring device using, encoding or streaming techniques to reduce the volume of the data, thereby reducing the need to have sophisticated monitoring devices. The invention may be used in several monitoring applications such as ambulatory or walking ECG monitoring (a/k/a Holter monitoring). In ambulatory ECG applications data is usually reviewed by superimposing current and previous QRS complex data to identify changes over time. In one embodiment of the invention, data is transferred at full resolution once to a main server and then the superimposition of the data is encoded using MPEG compression. The MPEG image of the data is substantially smaller yet offers the same degree of functionality since the MPEG image stream to the reviewer looks the same as the superimposition of the raw data. This improvement also uses fewer computing resources for playback. This is also applicable to full disclosure review for Holter monitoring.
The invention is also applicable to 12 or 15-lead ECG data monitoring. Raw sensor data is transformed into formatted images and then the formatted images are encoded as an MPEG video stream. The formatting and encoding condenses a very large amount of data into a very small data set that can be easily displayed on any computer. The invention also takes advantage of frame-by-frame review of the image supported by the MPEG format to permit the clinician to view changes in the ECG over time.
Yet another application of the invention involves generating a continuous display of waveforms. In this embodiment of the invention, data is encoded as a stream of digital video and/or audio depending on the type of raw signal. Preferably, the data is encoded using difference-based encoding, such as MPEG encoding. Encoding the data in this way makes it possible to perform data analysis on a wide variety of workstations, not just high-performance machines.
As is apparent from the above, it is an advantage of the present invention to provide a method and system of encoding physiological data to reduce the amount of data processed by analysis devices. Other features and advantages of the present invention will become apparent by consideration of the detailed description and accompanying drawings.